NFS (Network File System), which is a distributed file system and protocols defined in RFC (Request for Comments) 3530 and the like by IETF (Internet Engineering Task Force), is widely used. The distributed file system is a network file system where a single file system is physically distributed in a plurality of computer nodes, and use of the NFS makes it possible to store a file into a storage device distributed over a network and refer to a file of the storage device. To use a storage device distributed over a network, a technique of managing a file storage area is required. The following patent literatures are disclosed as a technique of managing a file storage area.
Patent Literature 1 discloses that there are included a table that stores the names of all files which exist in one directory with a full path and further stores information about the storage areas of the respective files in a storage device in association with the file names, and a search means that, when an input file name has a full path, searches the table using the input file name with the full path, and retrieves information about the storage area of the input file name in the storage device. In this case, the input file name as viewed by a user or program has no difference from a typical file system having a hierarchical structure and therefore an external multi-layered structure can be maintained, and, because all file names which exist in one directory are managed in one table, an internally flat file management can be made.
Patent Literature 2 discloses that there are included an entry management means that modifies a table to manage the ancestral relationship of entries at the time registering, deleting, or updating ID of an entry existing in a directory hierarchy, a filtering search means that searches for an entry by attribute conditions, and a scope determination means that performs a limited-scope search using the table of the ancestral relationship of entries, and, at the time of directory search, the filtering search means acquires entries that satisfy the attribute conditions, and the scope determination means narrows down the entries to the entry that satisfies the scope conditions.
Patent Literature 3 discloses that, in a processor, an index generation unit generates an index indicating file management information of a file to be read from a file name representing the file to be read by using a function in which a file name and an index are in one-to-one correspondence, and an index file management information associating unit reads the file management information corresponding to the index generated by the index generation unit from a file management information array in which file management information are arranged in order of index and obtains a storage area in a storage device related to the file to be read which is designated by the file management information.